Small volume electroplating cell

ABSTRACT

A method and apparatus for plating a metal onto a substrate. The apparatus generally The apparatus generally includes a substrate support member configured to support a substrate during a plating process, a cathode clamp ring detachably positioned to circumscribe a perimeter of the substrate and a movable anode assembly disposed above the substrate, wherein the anode assembly is movable in a direction generally perpendicular the substrate. The apparatus generally further includes a fluid inlet formed through the anode assembly, the fluid inlet being configured to supply a plating solution to the processing area sufficient to electrically connect the anode assembly to the substrate. The method generally includes supplying a plating solution to a processing chamber, the processing chamber being defined by a movable anode assembly disposed above the substrate and a cathode clamp ring detachably positioned to circumscribe the perimeter of the substrate, wherein the plating solution is supplied at a rate sufficient to electrically connect the anode assembly to the substrate and plating a metal from the plating solution onto the substrate.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] Embodiments of the present invention generally relate todeposition of a metal layer onto a substrate. More particularly, theembodiments of the present invention relate to electroplating a metallayer onto a substrate.

[0003] 2. Description of the Related Art

[0004] Metallization for sub-quarter micron sized features is afoundational technology for present and future generations of integratedcircuit manufacturing processes. In devices such as ultra large scaleintegration-type devices, i.e., devices having integrated circuits withmore than a million logic gates, the multilevel interconnects that lieat the heart of these devices are generally formed by filling highaspect ratio interconnect features with a conductive material, such ascopper or aluminum. Conventionally, deposition techniques such aschemical vapor deposition (CVD) and physical vapor deposition (PVD) havebeen used to fill these interconnect features. However, as interconnectsizes decrease and aspect ratios increase, void-free interconnectfeature fill via conventional metallization techniques becomesincreasingly difficult. As a result thereof, plating techniques, such aselectrochemical plating (ECP) and electroless plating, for example, haveemerged as viable processes for filling sub-quarter micron sized highaspect ratio interconnect features in integrated circuit manufacturingprocesses.

[0005] In an ECP process sub-quarter micron sized high aspect ratiofeatures formed on a substrate surface may be efficiently filled with aconductive material, such as copper, for example. ECP plating processesare generally two stage processes, wherein a seed layer is first formedover the surface features of the substrate, and then the surfacefeatures of the substrate are exposed to an electrolyte solution whilean electrical bias is simultaneously applied between the substrate andan anode positioned within the electrolyte solution. The electrolytesolution is generally rich in ions to be plated onto the surface of thesubstrate. Therefore, the application of the electrical bias causesthese ions to be urged out of the electrolyte solution and to be platedas a metal on the seed layer. The plated metal, which may be copper, forexample, grows in thickness and forms a copper layer that fills thefeatures formed on the substrate surface.

[0006] Present designs of cells for electroplating a metal onsemiconductor substrates are generally based on a fountain plater typeconfiguration. FIG. 1 illustrates a cross sectional view of a simplifiedexemplary fountain plater. Generally, the fountain plater 10 includes anelectrolyte container 12 having a top opening, a substrate holder 14disposed above the electrolyte container 12, an anode 16 disposed at abottom portion of the electrolyte container 12, and a cathode 20contacting the substrate 18. The cathode 20 includes a plurality ofcontact pins distributed about the peripheral portion of the substrate18 to provide an electrical bias to the substrate surface. Thesemiconductor substrate 18 is generally positioned a fixed distanceabove the electrolyte container 12, and the electrolyte generallyimpinges perpendicularly on the substrate plating surface. Because ofthe possible dispersion effects of the electrical current at the exposededges of the substrate 18 and the possible non-uniform flow of theelectrolyte, the fountain plater 10 may provide non-uniform currentdistribution, particularly at the region near the edges and at thecenter of the substrate 18, which may result in non-uniform plating onthe substrate. The electrolyte flow uniformity at the center of thesubstrate 18 can be improved by rotating the substrate 18. However, theplating uniformity still may deteriorate as the boundaries or edges ofthe substrate are approached.

[0007] Therefore, there remains a need for a reliable, consistent copperelectroplating technique to deposit and form copper layers onsemiconductor substrates having nanometer-sized, high aspect ratiofeatures. There is also a need for a face-up electroplating system thatallows fast substrate processing and increases throughput with a smallvolume of plating solution. Furthermore, there is a need for anapparatus for delivering a uniform electrical power distribution to asubstrate surface and a need for an electroplating system that providesuniform deposition on the substrate surface.

SUMMARY OF THE INVENTION

[0008] Embodiments of the invention generally include an apparatus forplating a metal onto a substrate surface. The apparatus generallyincludes a substrate support member configured to support a substrateduring a plating process, a cathode clamp ring detachably positioned tocircumscribe a perimeter of the substrate and a movable anode assemblydisposed above the substrate, wherein the anode assembly is movable in adirection generally perpendicular the substrate. The apparatus generallyfurther includes a fluid inlet formed through the anode assembly, thefluid inlet being configured to supply a plating solution to theprocessing area sufficient to electrically connect the anode assembly tothe substrate.

[0009] Embodiments of the invention further include a method for platinga metal onto a substrate. The method generally includes supplying aplating solution to a processing chamber, the processing chamber beingdefined by a movable anode assembly disposed above the substrate and acathode clamp ring detachably positioned to circumscribe the perimeterof the substrate, wherein the plating solution is supplied at a ratesufficient to electrically connect the anode assembly to the substrateand plating a metal from the plating solution onto the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] So that the manner in which the above recited features of thepresent invention are attained and can be understood in detail, a moreparticular description of the invention, briefly summarized above, maybe had by reference to the embodiments thereof which are illustrated inthe appended drawings. It is to be noted, however, that the appendeddrawings illustrate only typical embodiments of this invention and aretherefore not to be considered limiting of its scope, for the inventionmay admit to other equally effective embodiments.

[0011]FIG. 1 (Prior Art) illustrates a cross-sectional view of anexemplary fountain plater.

[0012]FIG. 2 illustrates a cross-sectional view of an exemplary platingcell.

[0013]FIG. 3 illustrates a cross-sectional view of an exemplary anodeassembly.

[0014]FIG. 4 illustrates a cross-sectional view of another anodeassembly.

[0015]FIG. 5 illustrates a cross-sectional view of another anodeassembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0016]FIG. 2 illustrates a cross-sectional view of an exemplary platingcell 100 with a substrate 116 in a processing position. The plating cell100 generally includes an enclosure 126 having a substrate supportmember 102 and an anode assembly 104. The substrate support member 102generally includes a conductive base plate 130 providing a cathodeconnection to a cathode clamp ring 108. The substrate support member 102is generally disposed in a bottom portion of the enclosure 126. Theanode assembly 104, discussed in further detail below, is electricallyconnected to a power supply 106 via an electrical line 128. The platingcell 102 may further include a vacuum chuck to secure the substrate 116onto a substrate supporting surface 132 on the substrate support member102 during processing.

[0017] In the loading position, the cathode clamp ring 108, which may besupported by an annular catch cup 110, is generally disposed in a middleportion of the plating cell 100 between the substrate support member 102and the anode assembly 104. The cathode clamp ring 108 is positioned inthe plating cell 100 such that the movement of the substrate supportmember 102 from a load/transfer position (not shown), to the processingposition lifts the cathode clamp ring 108 slightly off the catch cup110. The load/transfer position is discussed in detail in U.S. Pat. No.6,416,647, filed on Apr. 19, 1999, which is hereby incorporated byreference.

[0018] The cathode clamp ring 108 preferably includes an outer portionhaving a downwardly sloping surface 166 that overlaps an inner terminus168 of the catch cup 110 to assist the plating solution flow into thecatch cup 110. The inner terminus 168 includes a ridge 170 correspondingto a recess 172 on the bottom surface 174 of the cathode clamp ring 108.The ridge 170 supports the cathode clamp ring 108 when the substratesupport member 102 is not engaged in a deposition position. When thesubstrate support member 102 is engaged in the deposition position, thecathode clamp ring 108 is lifted from the ridge 170 and is supported onthe substrate deposition surface 176.

[0019] The electrical power is delivered by the cathode clamp ring 108to the substrate deposition surface 176 through a contact portion 178 ofthe cathode clamp ring 108. To provide electrical power to the cathodeclamp ring 108, one or more cathode contacts 180 are fixedly secured toa bottom surface 146 of the conductive base plate 130 of the substratesupport member 102 and extend radially outward to electrically contact abottom surface 174 of the cathode clamp ring 108. Upon rotation, theelectrical power is conducted through the rotating shaft 134 to theconductive base plate 130, then through one or more cathode contacts 180secured onto the conductive base plate 130, and then to a bottom surface174 of the cathode clamp ring 108. Alternatively, the cathode clamp ring108 is fixedly connected to the power supply 106 through connectionwires (not shown).

[0020] The rotating shaft 134 extends through a lift pin platform 136having a plurality of lift pins 138 disposed thereon. A lift platformactuator 142 moves the lift pin platform 136 vertically to lift andlower a substrate 116 for transfer into and out of the plating cell 100.A flexible bellow 144, preferably made of polyethylene, is disposedaround each lift pin 138, to provide a splash seal against platingsolutions, rinsing solutions, and other processing chemicals. Theflexible bellow 144 is attached from a top surface of the lift pinplatform 136 to a bottom surface of the conductive base plate 146 of thesubstrate support member 102. The flexible bellow 144 compresses whenthe lift pin platform 136 is elevated by the lift platform actuator 142and stretches when the lift pin platform 136 is resting on a platformridge 148. Each flexible bellow 144 also maintains a seal when subjectedto a slight side load, such as when the substrate support member 102rotationally accelerates or decelerates.

[0021] To prevent plating solutions, rinsing solutions, and otherprocess chemicals from contacting components disposed in the centralportion of the plating cell 100, such as the lift platform actuator 142and the shaft sleeve 150, a splash guard 152 is generally attached to anouter portion of a lower surface of the lift pin platform 136. Thesplashguard 152 includes a cylindrical downward extension that isdisposed radially outward of an upwardly extending inner container wall154. The inner container wall 154 is a cylindrical upward extension fromthe enclosure bottom 156 of the plating cell 100 that holds the processsolutions to be pumped out of the system through a solution outlet 114.

[0022] To provide rotational movement to the substrate support member102, a rotary actuator 158 is disposed on an actuator platform 160 andconnected to the rotating shaft 134. The rotary actuator 158 rotates therotating shaft 134 freely within the shaft sleeve 150. Duringdeposition, the rotary actuator 158 rotates or oscillates the substratesupport member 102 about a central axis through the rotating shaft 134.Generally, the rotary actuator 158 rotates the support member 102 atbetween about 10 revolutions or cycles per minute to about 50 RPM orcycles per minute. The rotation or oscillation of the substrate supportmember 102 provides uniform exposure of the plating solution to thesubstrate deposition surface 176 promoting uniform metal deposition. Inthe alternative, the anode assembly 104 may be rotated. Depositionuniformity is further promoted by continuous cathode electrical contactprovided by the cathode clamp ring 108. The cathode clamp ring 108operates to distribute a uniform current density across the substratedeposition surface 176.

[0023] To move the substrate support member 102 vertically, a verticalactuator 162 extends and retracts a shaft 164 connected to the actuatorplatform 160. The vertical actuator 162 is disposed outside of the cell100 on the cell bottom 156, and the shaft 164 extends through the cellbottom 156 and is attached to a bottom surface of the actuator platform160. These actuators may be fluid cylinders, screw-type actuators, orany other actuator capable of producing longitudinal movements. Inaddition, a substrate transfer actuator 122 vertically adjusts the anodeassembly 104 to set an anode assembly 104 to substrate 116 distance. Thedistance may be from about 2 mm to about 20 mm. The anode assembly 104may be sized to recess within the contact ring 108 upon verticaladjustment, e.g., during plating, so that the anode assembly 104 is inelectrical contact with the plating solution. In addition, platingsolution may flow through the anode assembly 104 to provide additionalplating solution or to provide movement within the existing platingsolution. Alternatively, the anode assembly 104 may be sized to restupon the contact ring 108 upon vertical adjustment. When the anodeassembly 104 rests upon the contact ring 108, an insulator may beutilized to separate the anode assembly 104 and the contact ring 108.

[0024] The cell 100 additionally includes a sidewall 124 having a slit118 formed therein for receiving and discharging a substrate 116, e.g.,loading and transferring the substrate 116. The plurality of lift pins136 extends through vertical bores in the substrate support member 102and lifts the substrate 116 above a robot blade (not shown). The robotblade then retracts out of the cell 100 and the slit valve 120 closesthe slit opening 118. Once the substrate 116 is in the processingposition, a plating solution pump (not shown), which is connected to aplating solution inlet 112, pumps plating solution from a platingsolution reservoir (not shown) into the plating cell 100. Generally, aplating solution outlet 114 is connected to a plating solution drain(not shown) formed in the catch cup 110 to return the plating solutionback to the plating solution reservoir to be re-circulated to theplating cell 100.

[0025] The plating solution fills a processing area defined by thesubstrate 116, i.e., the processing area bottom, and the contact ring108, i.e., the sidewalls. Therefore, the volume of the processing areaand the resulting volume of the plating solution utilized are dependentupon the size of the substrate 116 and the height of the contact ring108. In addition, the volume is dependent upon the distance of the anodeassembly 104 from the substrate 116. Generally the anode assembly 104 isfrom about 2 mm to about 20 mm from the substrate 116. Preferably, theanode assembly 104 is from about 2 mm to about 10 mm from the substrate116.

[0026]FIG. 3 illustrates a cross-sectional view of an exemplary anodeassembly 200. The anode assembly 200 may be used in the plating cell 100described above, or another plating cell capable of processingsemiconductor substrates in the face-up position. The anode assembly 200and the substrate 116 and clamp ring 108 define a cell chamber 208,e.g., a processing area. The cell chamber 208 generally has a volume offrom about 0.5 L to about 1.9 L.

[0027] The anode assembly 200 generally includes an anode plate 202 anda hood 204. The anode plate 202 generally has a circular cross-section.The anode plate 202 preferably includes a consumable metal that candissolve in the electroplating solution to provide the metal particlesto be deposited onto the substrate deposition surface. The hood 204,which is electrically insulated from the anode plate 202, depends fromthe outer periphery of the anode plate 202 and may be made of anodicmaterial, which is the same or different from the material of the anodeplate 202. For example, the anode plate 202 may be formed of a meshmaterial. Alternatively, the anode plate 202 and hood 204 are each madeof consumable metal particles encased in a fluid permeable membrane suchas a porous ceramic plate. An alternative to the consumable anode plateis a non-consumable anode plate that is perforated or porous for passageof the electroplating solution therethrough. However, when anon-consumable anode plate is used, the electroplating solution requiresa metal particle supply to continually replenish the metal particles tobe deposited in the process.

[0028] As described above, the contact ring 108 is in electricalcommunication with the cathode terminal of a power supply (not shown).The power source discussed in reference to FIG. 2 generally includescontrols for varying the voltage and polarity of the anode plate 202 andthe hood 204. For example, to ensure plating in a central portion of thesubstrate, the hood 204 may be electrically isolated to prevent ionsfrom plating on the hood 204.

[0029] The hood 204 generally is secured to the anode plate 202 by aninsulating ring 206. The hood 204 is sized to substantially cover thesubstrate 116 and the clamp ring 108 from the outer edges of the anodeplate 202 extending downward towards the substrate 116.

[0030] The flow of electrolyte through the processing chamber 208 iscontrolled by the size of an annular opening 210, e.g., the distancebetween the hood 204 and the clamp ring 108. The annular opening 210 issized in relation to the electrolyte flow rate to maintain theelectrolyte in the chamber 208 at a predetermined level during theplating process. Generally, the flow of plating solution continuesduring plating to retain electrical contact between the anode plate 202and the substrate 116. In addition, the flow of electrolyte into theprocessing chamber 208 is generally equal to the flow of electrolyte outof the processing chamber through the annular opening 210 and theconsumption of electrolyte due to plating on the substrate. Generally,the processing chamber 208 is full of electrolyte throughout plating tomaintain an electrical connection between the anode and the substrate.

[0031] In operation, the plating cell provides a small volume(electrolyte volume) processing chamber 208 that may be used for copperelectrochemical plating processes, for example. A substrate 116 is firstimmersed into a plating solution contained within the processing chamber208. Once the substrate is immersed in the plating solution, whichgenerally contains copper sulfate, chlorine, and one or more of aplurality of plating additives (levelers, suppressors, accelerators,etc.) configured to control plating parameters, an electrical platingbias is applied between a seed layer on the substrate and the anode 202positioned above the substrate 116. The electrical plating biasgenerally operates to cause metal ions in the plating solution todeposit on the cathodic substrate surface 116. The plating solution iscontinually circulated through the processing chamber 208 via fluidinlets and outlets.

[0032]FIG. 4 illustrates a cross-sectional view of another anodeassembly 300. The embodiment shown in FIG. 3 includes the samecomponents as the embodiment shown in FIG. 2, except that the anodeplate 304 does not include a hood. Thus, the cell chamber 302 is definedby the downwardly facing surface of the anode plate 304, the upwardlyfacing surface of the substrate 116, and the clamp ring 108, e.g., theclamp ring 108 operates as sidewalls for the chamber 302, therebydefining the volume of the chamber 302. The distance of the anode plate304 from the substrate 116 is generally minimized. For example, thedistance may be from about 2 mm to about 20 mm, resulting in a smallchamber volume. Alternatively, the distance may be from about 2 mm toabout 10 mm. The precise volume of the chamber is determined by thevertical actuator setting.

[0033]FIG. 5 illustrates yet another embodiment of an anode assembly400. The anode assembly 400 includes an anode plate 402. The anode plate402 generally includes a plurality of annular anode segments that areseparated by insulators 404. The insulators 404 may be annular spaces,plastic rings, or other means capable of insulating the anode segmentsfrom one another. The individual anode segments allow selective platingoperation by providing individual voltage control for each anodesegment. Selective operation provides control over the flow of cationsadhering and flowing to the cathode/substrate 116, thereby resulting inuniform plating upon the substrate 116. Although the anode assembly 400may be used alone, the anode assembly 400 may also be used inconjunction with either of the embodiments illustrated in FIGS. 2 and 3.

[0034] While the foregoing is directed to embodiments of the presentinvention, other and further embodiments of the invention may be devisedwithout departing from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. An apparatus for plating a metal onto a substratesurface, comprising: a substrate support member configured to support asubstrate during a plating process; a cathode clamp ring detachablypositioned to circumscribe a perimeter of the substrate; a movable anodeassembly disposed above the substrate, wherein the anode assembly ismovable in a direction generally perpendicular the substrate; and afluid inlet formed through the anode assembly, the fluid inlet beingconfigured to supply a plating solution to the processing areasufficient to electrically connect the anode assembly to the substrate.2. The apparatus of claim 1, wherein the movable anode assembly isconfigured to adjust a distance between an anode plate of the anodeassembly and the substrate.
 3. The apparatus of claim 2, wherein thedistance is between about 2 mm and about 20 mm.
 4. The apparatus ofclaim 1, wherein movable anode assembly includes a disk shaped anodeplate surrounded by an annular hood member.
 5. The apparatus of claim 3,wherein the hood member is manufactured from an insulating material. 6.The apparatus of claim 4, wherein the hood member is manufactured from ametal and is connected to a power source to selectively control currentpassing between the anode plate and the substrate.
 7. The apparatus ofclaim 1, wherein movable anode assembly comprises a disk shaped anodeplate having an aperture formed therein, the aperture forming the fluidinlet.
 8. The apparatus of claim 7, wherein the anode plate ispositioned in parallel relationship to a plating surface of thesubstrate.
 9. The apparatus of claim 7, further comprising an actuatorconfigured to actuate the anode plate toward and away from thesubstrate.
 10. The apparatus of claim 1, wherein the cathode clamp ringis configured to be positioned over an upper perimeter surface of thesubstrate support member in a manner such that the cathode clamp ringelectrically engages the perimeter portion of the substrate and forms aprocessing volume above the substrate and within the clamp ring.
 11. Theapparatus of claim 10, wherein the processing volume is as deep as thecathode clamp ring is tall and is sized to receive an anode platetherein.
 12. A method for plating a metal onto a substrate, comprising:supplying a plating solution to a processing volume, the processingvolume being defined by a movable anode assembly disposed above thesubstrate and a cathode clamp ring detachably positioned to circumscribea perimeter of the substrate, wherein the plating solution is suppliedat a rate sufficient to electrically connect the anode assembly to thesubstrate; and plating a metal from the plating solution onto thesubstrate.
 13. The method of claim 12, further comprising moving theanode assembly to define a distance between the anode plate and theplating surface.
 14. The method of claim 12, wherein the anode assemblycomprises an anode plate including a plurality of metal segments, theplurality of metal segments being separately controlled by a powersource to provide uniform metal deposition.
 15. The method of claim 14,wherein the plurality of metal segments are separated by an insulatingmaterial.
 16. The method of claim 12, wherein the anode assembly furthercomprises a hood depending from the periphery of the anode plate. 17.The method of claim 16, further comprising releasing electrolyte fromthe processing chamber through an annular opening, the annular openingbeing defined by a distance between the hood and the cathode clamp ring.18. The method of claim 17, further comprising supplying platingsolution to the processing chamber at a rate essentially equal to therate of release.
 19. The method of claim 12, further comprising rotatingthe substrate.
 20. The method of claim 12, further comprising adjustingthe anode assembly to form a cell chamber having a volume of from about0.5 L to about 1.9 L.
 21. The method of claim 14, wherein the distancebetween the substrate and the anode plate is between about 2 mm and 20mm.
 22. The method of claim 14, wherein the distance between thesubstrate and the anode plate is between about 2 mm and about 10 mm. 23.An electrochemical processing cell, comprising: a substrate supportmember having a circular upper substrate support surface formed thereon;an annular cathode contact ring configured to releasably engage an outerperimeter of the substrate support surface and electrically contact asubstrate positioned thereon; and a disk shaped anode configured to bereceived within an inner diameter of the annular cathode contact ring,the disk shaped anode being movable between an processing position and aloading position.
 24. The processing cell of claim 23, wherein the diskshaped anode further comprises a fluid inlet configured to deliver aprocessing fluid to a processing volume defined by the anode, thecathode contact ring, and the substrate.
 25. The processing cell ofclaim 23, wherein the contact ring forms an annular wall above thesubstrate, the annular wall being configured to maintain a volume of aplating solution therein.
 26. The processing cell of claim 23, whereinthe anode further comprises a hood member.